Preliminary results suggest that isolated and cultured bovine chromaffin cells possess a potassium conductance that plays an important role in the maintenance of resting membrane potential. Blockade of this current would lead to depolarization of the chromaffin cell and opening of voltage-dependent calcium channels, calcium entry and catecholamine(ca) secretion. The fact that CA secretion evoked by tetra ethylammonium (TEA) from chromaffin cells is calcium-dependent, blocked by high magnesium and organic calcium antagonists supports the previous sequence of events.